EP0569769A1 - Optical telecommunications system with monitoring device for avoiding strong pulses - Google Patents

Optical telecommunications system with monitoring device for avoiding strong pulses Download PDF

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Publication number
EP0569769A1
EP0569769A1 EP93106767A EP93106767A EP0569769A1 EP 0569769 A1 EP0569769 A1 EP 0569769A1 EP 93106767 A EP93106767 A EP 93106767A EP 93106767 A EP93106767 A EP 93106767A EP 0569769 A1 EP0569769 A1 EP 0569769A1
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EP
European Patent Office
Prior art keywords
optical
monitoring device
pump light
amplifier
light source
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Granted
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EP93106767A
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German (de)
French (fr)
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EP0569769B1 (en
Inventor
Rolf Dr. Heidemann
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Alcatel Lucent SAS
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Alcatel SEL AG
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/29—Repeaters
    • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
    • H04B10/293—Signal power control
    • H04B10/2931—Signal power control using AGC
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
    • H01S3/1001—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by controlling the optical pumping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/29—Repeaters
    • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
    • H04B10/2912—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
    • H01S3/10015—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by monitoring or controlling, e.g. attenuating, the input signal

Definitions

  • the invention relates to an optical communication system according to the preamble of claim 1.
  • Such systems are well known.
  • Such a system is described, for example, in Wedding, B. et al "10 Gbit / s To 260,000 Subscribers Using Optical Amplifier Distribution Network”; Contribution for ICC / Supercom'92, Optical Communications 300 Level Session "Impact of Optical Amplifiers on Network Architectures”.
  • a fiber-optic amplifier is shown in detail, for example, in EP 0457 349 A2.
  • fiber-optic amplifiers generally serve to amplify an optical signal carried in an optical waveguide section.
  • Fiber optic amplifiers are connected to an optical fiber in which optical signals are carried by splices or optical connectors. Individual optical fibers are also connected using splices or optical connectors.
  • An optical fiber amplifier section contained in a fiber optic amplifier is coated with ions of a rare earth element, e.g. He 3+, endowed.
  • a pump light emitted by a pump light source is coupled into the amplifying optical waveguide piece via a coupler.
  • the pump light converts the erbium ions from a ground state to an excited state, from which they return to the ground state, either through spontaneous or stimulated emission.
  • the stimulated emission is excited by the optical signal to be amplified which runs through the amplifying optical waveguide piece.
  • the spontaneous emission is also amplified in the amplifying optical waveguide piece; this amplified spontaneous emission (ASE) spreads in and against the direction of transmission of the optical signal and is the cause of the noise occurring in a fiber optic amplifier.
  • ASE amplified spontaneous emission
  • optical isolators there are differences in the literature regarding the use of optical isolators.
  • an optical isolator is used at the input and output.
  • an optical isolator is used only at the output.
  • Optical isolators ensure stable amplifier operation, but their insertion loss worsens the noise characteristics of the amplifier. Dispensing with the optical isolator at the signal input therefore has a favorable effect on the costs and the noise properties of the fiber optic amplifier.
  • a pump light coupler is arranged in front of an amplifying fiber piece based on the direction of transmission of the optical signal. However, based on the direction of transmission, it can also be arranged behind the reinforcing fiber piece. The arrangement of the coupler is irrelevant for the present invention.
  • an optical waveguide section 1 for example an amplifying optical waveguide section 3 doped with Er3+ ions, a pumping light source 4 with a laser diode, hereinafter also referred to as a pumping laser, which pumps the pumping light for the fiber optic Generates amplifier and a pump light coupler 5, which makes it possible to couple the pump light into the amplifying optical waveguide section 3.
  • an optical waveguide section 1 for example an amplifying optical waveguide section 3 doped with Er3+ ions
  • a pumping light source 4 with a laser diode, hereinafter also referred to as a pumping laser which pumps the pumping light for the fiber optic Generates amplifier
  • a pump light coupler 5 which makes it possible to couple the pump light into the amplifying optical waveguide section 3.
  • the fiber optic amplifier is connected to an optical fiber link via an input E and an output A.
  • An input power available at input E is amplified.
  • An optical isolator 6 protects the fiber optic amplifier from the effects of a subsequent optical fiber link or amplifier stage.
  • the addition of the fiber optic amplifier according to the invention consists in that a part of the input power is decoupled via a coupler 8 and fed to a monitoring device 7 which switches off the pump laser 4 when the input power drops or controls an optical switch 12 so that no pump light enters the amplifying optical waveguide piece 3 arrives.
  • system components can be damaged when opening an optical connector.
  • the input power of the fiber optic amplifier which is denoted by P in , drops to zero.
  • the stimulated emission stops in the amplifying piece of optical waveguide; however, the spontaneous emission that always takes place continues to occur.
  • the time course of the attenuation D, the reflection R and the input power P in the fiber-optic amplifier could be determined when the optical waveguide was interrupted, as shown in FIG. 2.
  • the point of interruption is the starting point for reflections due to the jump in the refractive index that occurs there, so that the light of the spontaneous emission is reflected there and passes through the amplifying optical waveguide piece in the signal direction.
  • the amplifying optical waveguide piece is in an excited state, since the pump laser pumps independently of the input thereof and, because of the missing signal, there is no stimulated emission.
  • the reflected light reaches the reinforcing optical waveguide piece in this state of maximum population inversion and thereby triggers the release of the stored energy. A huge pulse is emitted.
  • the invention is based on the knowledge that the occurring reflection R only occurs after a delay time ⁇ after which the input power has dropped due to the increase in the damping D. This makes it possible according to the invention to derive a control signal from the input power.
  • the function of the monitoring device according to the invention is to interrupt the current path or the light path of the pump laser within the time ⁇ as soon as the input power of the fiber optic amplifier falls below a certain threshold value. Measurements have shown that the time ⁇ is approximately 1 ms and is therefore sufficiently long for the pump laser to be switched off in good time or the pump laser light path to be interrupted in good time.
  • FIG. 3 An exemplary embodiment of how the optical signal derived from the input power is processed is shown in FIG. 3. From the output of the fiber optic coupler it arrives at a photodetector 71. Its electrical output signal is amplified by an amplifier 72 and fed to a threshold switch 73 which compares the output voltage U of the amplifier with a reference voltage U ref . Does that fall Amplifier output voltage below a threshold, which is given by the reference voltage, outputs the control device, which consists of components 71, 72 and 73, a control signal. A subsequent amplifier 9 thus controls a transistor 10 which is in the current path of the pump laser 4. As a result, the current path of the pump laser can be interrupted and the light emission of the pump laser can be switched off.
  • FIG. 4 shows a possibility in which the monitoring device 7 controls an optical switch 12 in such a way that it interrupts the light path of the pump laser.
  • an optical switch is shown, for example, in Siemens telcom report 6, April 1983, supplement “Message transmission with light", pp. 205-208.

Abstract

If the optical isolator at the input of optical telecommunication systems with fibre-optical amplifiers is omitted for cost reasons and because of the impairment of the noise characteristics caused by the insertion loss, a strong pulse can be emitted at the input when an optical plug-in connector is opened. To avoid this, a monitoring device (7) is used which rapidly disconnects the current of the pumping laser (4) or interrupts the optical path of the pumping laser (4) when the input power of the fibre-optical amplifier (4, 5, 3, 6) drops below a certain threshold. <IMAGE>

Description

Die Erfindung betrifft ein optisches Nachrichtenübertragungssystem nach dem Oberbegriff des Anspruchs 1. Solche Systeme sind hinreichend bekannt. Ein solches System wird beispielsweise in Wedding, B. et al "10 GBit/s To 260 000 Subscribers Using Optical Amplifier Distribution Network"; Contribution for ICC/Supercom'92, Optical Communications 300 Level Session "Impact of Optical Amplifiers on Network Architectures", gezeigt. Einen faseroptischen Verstärker im Detail zeigt beispielsweise EP 0457 349 A2.The invention relates to an optical communication system according to the preamble of claim 1. Such systems are well known. Such a system is described, for example, in Wedding, B. et al "10 Gbit / s To 260,000 Subscribers Using Optical Amplifier Distribution Network"; Contribution for ICC / Supercom'92, Optical Communications 300 Level Session "Impact of Optical Amplifiers on Network Architectures". A fiber-optic amplifier is shown in detail, for example, in EP 0457 349 A2.

Faseroptische Verstärker dienen in einem optischen Nachrichtenübertragungssystem allgemein dazu, ein in einer Lichtwellenleiterstrecke geführtes optisches Signal zu verstärken.In an optical communication system, fiber-optic amplifiers generally serve to amplify an optical signal carried in an optical waveguide section.

Faseroptische Verstärker werden mit einem Lichtwellenleiter, in dem optische Signale geführt werden, durch Spleiße oder optische Steckverbinder verbunden. Auch die Verbindung einzelner Lichtwellenleiter erfolgt durch Spleiße oder optische Steckverbinder.Fiber optic amplifiers are connected to an optical fiber in which optical signals are carried by splices or optical connectors. Individual optical fibers are also connected using splices or optical connectors.

Ein in einem faseroptischen Verstärker enthaltenes verstärkendes Lichtwellenleiterstück ist mit Ionen eines Seltenerd-Elements, z.B. Er ³⁺, dotiert. Ein von einer Pumplicht-Quelle emittiertes Pumplicht wird über einen Koppler in das verstärkende Lichtwellenleiterstück eingekoppelt. Durch das Pumplicht werden die Erbium-Ionen von einem Grundzustand in einen angeregten Zustand überführt, von dem aus sie, entweder durch spontane oder stimulierte Emission, wieder in den Grundzustand übergehen. Die stimulierte Emission wird durch das durch das verstärkende Lichtwellenleiterstück laufende zu verstärkende optische Signal angeregt. Die spontane Emission wird in dem verstärkenden Lichtwellenleiterstück ebenfalls verstärkt; diese verstärkte spontane Emission (engl.: amplified spontaneous emission, ASE) breitet sich in und entgegen der Übertragungsrichtung des optischen Signals aus und ist ursächlich für das in einem faseroptischen Verstärker auftretende Rauschen.An optical fiber amplifier section contained in a fiber optic amplifier is coated with ions of a rare earth element, e.g. He ³⁺, endowed. A pump light emitted by a pump light source is coupled into the amplifying optical waveguide piece via a coupler. The pump light converts the erbium ions from a ground state to an excited state, from which they return to the ground state, either through spontaneous or stimulated emission. The stimulated emission is excited by the optical signal to be amplified which runs through the amplifying optical waveguide piece. The spontaneous emission is also amplified in the amplifying optical waveguide piece; this amplified spontaneous emission (ASE) spreads in and against the direction of transmission of the optical signal and is the cause of the noise occurring in a fiber optic amplifier.

Bezüglich der Verwendung von optischen Isolatoren gibt es in der Literatur Unterschiede. In der oben genannten Patentschrift wird jeweils am Ein- und Ausgang ein optischer Isolator eingesetzt. In der ebenfalls oben genannten Schrift von Wedding, B.; et al, wird nur am Ausgang ein optischer Isolator verwendet. Optische Isolatoren sorgen für stabilen Verstärkerbetrieb, verschlechtern aber durch ihre Einfügedämpfung die Rauscheigenschaften des Verstärkers. Ein Verzicht auf den optischen Isolator am Signaleingang wirkt sich daher günstig auf die Kosten und die Rauscheigenschaften des faseroptischen Verstärkers aus.There are differences in the literature regarding the use of optical isolators. In the patent mentioned above, an optical isolator is used at the input and output. In the same document by Wedding, B .; et al, an optical isolator is used only at the output. Optical isolators ensure stable amplifier operation, but their insertion loss worsens the noise characteristics of the amplifier. Dispensing with the optical isolator at the signal input therefore has a favorable effect on the costs and the noise properties of the fiber optic amplifier.

Es ist daher wünschenswert, den optischen Isolator am Eingang wegzulassen. Dabei hat sich jedoch gezeigt, daß beim Öffnen eines optischen Steckverbinders Systemkomponenten, z.B. Photodioden, beschädigt werden können.It is therefore desirable to omit the optical isolator at the entrance. It has been shown, however, that system components, for example photodiodes, can be damaged when an optical connector is opened.

Es ist die Aufgabe der Erfindung, ein optisches Nachrichtenübertragungssystem der eingangs genannten Art anzugeben, bei dem die Gefahr einer Beschädigung von Systemkomponenten beim Öffnen eines optischen Steckverbinders vermieden wird.It is the object of the invention to provide an optical communication system of the type mentioned in the introduction, in which the risk of damage to system components when an optical connector is opened is avoided.

Die Aufgabe wird wie in Patentanspruch 1 angegeben gelöst. Weiterbildungen ergeben sich aus den Unteransprüchen.The object is achieved as indicated in claim 1. Further training results from the subclaims.

Die Erfindung wird nun anhand der Zeichnungen näher erläutert. Es zeigen:

Fig. 1
ein Ausführungsbeispiel eines faseroptischen Verstärkers mit erfindungsgemäßer Überwachungsvorrichtung,
Fig. 2
den zeitlichen Verlauf der Dämpfung D, der Reflexion R und der Eingangsleistung Pin des faseroptischen Verstärkers beim Auftrennen des optischen Steckverbinders,
Fig. 3
ein Beispiel, wie die in Fig. 1 gezeigte Überwachungsvorrichtung zur Stromunterbrechung der Pumplicht-Quelle ausgeführt sein kann,
Fig. 4
ein weiteres Ausführungsbeispiel der in Fig. 1 gezeigten Überwachungsvorrichtung zur Unterbrechung des Lichtweges der Pumplicht-Quelle.
The invention will now be explained in more detail with reference to the drawings. Show it:
Fig. 1
An embodiment of a fiber optic amplifier with a monitoring device according to the invention,
Fig. 2
the time course of the attenuation D, the reflection R and the input power P in the fiber optic amplifier when the optical connector is disconnected,
Fig. 3
1 shows an example of how the monitoring device shown in FIG. 1 can be designed to interrupt the current of the pump light source,
Fig. 4
a further embodiment of the monitoring device shown in Fig. 1 for interrupting the light path of the pump light source.

In Fig. 1 ist ein Pumplicht-Koppler bezogen auf die Übertragungsrichtung des optischen Signals vor einem verstärkenden Faserstück angeordnet. Er kann aber auch, bezogen auf die Übertragungsrichtung, hinter dem verstärkenden Faserstück angeordnet sein. Für die vorliegende Erfindung spielt die Anordnung des Kopplers keine Rolle.In Fig. 1, a pump light coupler is arranged in front of an amplifying fiber piece based on the direction of transmission of the optical signal. However, based on the direction of transmission, it can also be arranged behind the reinforcing fiber piece. The arrangement of the coupler is irrelevant for the present invention.

Ein faseroptischer Verstärker nach Fig. 1 besteht wie bekannte faseroptische Verstärker aus einem Lichtwellenleiterstück 1, einem beispielsweise mit Er³⁺-Ionen dotierten verstärkenden Lichtwellenleiterstück 3, einer Pumplicht-Quelle 4 mit Laserdiode, im folgenden auch als Pumplaser bezeichnet, die das Pumplicht für den faseroptischen Verstärker erzeugt und einem Pumplicht-Koppler 5, der es ermöglicht, das Pumplicht in das verstärkende Lichtwellenleiterstück 3 einzukoppeln.1 consists, like known fiber-optic amplifiers, of an optical waveguide section 1, for example an amplifying optical waveguide section 3 doped with Er³⁺ ions, a pumping light source 4 with a laser diode, hereinafter also referred to as a pumping laser, which pumps the pumping light for the fiber optic Generates amplifier and a pump light coupler 5, which makes it possible to couple the pump light into the amplifying optical waveguide section 3.

Über einen Eingang E und einem Ausgang A ist der faseroptische Verstärker mit einer Lichtwellenleiterstrecke verbunden. Eine am Eingang E zur Verfügung stehende Eingangsleistung wird verstärkt. Ein optischer Isolator 6 schützt den faseroptischen Verstärker vor Rückwirkungen von eine nachfolgenden Lichtwellenleiterstrecke oder Verstärkerstufe.The fiber optic amplifier is connected to an optical fiber link via an input E and an output A. An input power available at input E is amplified. An optical isolator 6 protects the fiber optic amplifier from the effects of a subsequent optical fiber link or amplifier stage.

Die erfindungsgemäße Ergänzung des faseroptischen Verstärkers besteht darin, daß ein Teil der Eingangsleistung über einen Koppler 8 ausgekoppelt wird und einer Überwachungsvorrichtung 7 zugeführt wird, die den Pumplaser 4 bei abfallender Eingangsleistung abschaltet oder einen optischen Schalter 12 so steuert, daß kein Pumplicht in das verstärkende Lichtwellenleiterstück 3 gelangt.The addition of the fiber optic amplifier according to the invention consists in that a part of the input power is decoupled via a coupler 8 and fed to a monitoring device 7 which switches off the pump laser 4 when the input power drops or controls an optical switch 12 so that no pump light enters the amplifying optical waveguide piece 3 arrives.

Durch die Abschaltbarkeit des Pumplasers bzw. die Unterbrechbarkeit des Lichtweges des Pumplichtes wird das folgende Problem gelöst.The following problem is solved by switching off the pump laser or interrupting the light path of the pump light.

Wie bereits erwähnt können unter Umständen Systemkomponenten beim Öffnen eines optischen Steckverbinders beschädigt werden.As already mentioned, system components can be damaged when opening an optical connector.

Es wurde erkannt, daß eine Beschädigung von Systemkomponenten durch Impulse hoher Energie erfolgt, die beim Öffnen eines optischen Steckverbinders entstehen. Das Entstehen dieser Riesenimpulse läßt sich wie folgt erklären. Im Normalfall sind Reflexionen, die an den optischen Steckverbindern auftreten gering und daher unproblematisch. Wird allerdings die Lichtwellenleiterstrecke im Betrieb durch Öffnen eines optischen Steckverbinders unterbrochen, fällt die Eingangsleistung des faseroptischen Verstärkers schlagartig auf Null ab. An einer solchen Unterbrechungsstelle kann Lichtleistung reflektiert werden. Da der Pumpvorgang unabhängig von der Eingangsleistung ist, wird in das Verstärkungsmedium ständig Energie gepumpt; es kommt zur völligen Besetzungsinversion. Durchläuft reflektiertes Licht, das z.B. von der spontanen Emission herrührt, das verstärkende Lichtwellenleiterstück, dessen laseraktive Substanz sich im invertierten Zustand befindet, wird die gespeicherte Energie schlagartig freigesetzt. Es kommt zur Emission eines Riesenimpulses, der eine Gefahr für nachfolgende Systemkomponenten, beispielsweise Photodetektoren, darstellt.It has been recognized that system components are damaged by high energy pulses that occur when an optical connector is opened. The emergence of these giant impulses can be explained as follows. In the normal case, reflections that occur at the optical connectors are low and therefore unproblematic. However, if the optical fiber link is interrupted during operation by opening an optical connector, the input power of the fiber optic amplifier suddenly drops to zero. Light power can be reflected at such an interruption point. Since the pumping process is independent of the input power, energy is constantly pumped into the gain medium; there is a complete inversion of the cast. If reflected light, which originates, for example, from the spontaneous emission, passes through the amplifying piece of optical waveguide, the laser-active substance of which is in the inverted state, the stored energy is suddenly released. A huge pulse is emitted, which poses a danger to subsequent system components, for example photodetectors.

Bei einer Unterbrechung der Lichtwellenleiterstrecke, beispielsweise zum Zeitpunkt t = T₀

Figure imgb0001
, fällt die Eingangsleistung des faseroptischen Verstärkers, die mit Pin bezeichnet ist, auf Null ab. In diesem Fall hört die stimulierte Emission im verstärkenden Lichtwellenleiterstück auf; die immer stattfindende spontane Emission erfolgt jedoch weiterhin.In the event of an interruption in the optical fiber link, for example at the time t = T₀
Figure imgb0001
 , the input power of the fiber optic amplifier, which is denoted by P in , drops to zero. In this case, the stimulated emission stops in the amplifying piece of optical waveguide; however, the spontaneous emission that always takes place continues to occur.

Aufgrund von Messungen an optischen Steckverbindern konnte der zeitliche Verlauf der Dämpfung D, der Reflexion R und der Eingangsleistung Pin des faseroptischen Verstärkers bei einer Unterbrechung des Lichtwellenleiters, wie in Fig. 2 gezeigt, ermittelt werden. Die Unterbrechungsstelle ist aufgrund des dort entstehenden Sprungs im Brechungsindex Ausgangspunkt für Reflexionen, so daß dort das Licht der spontanen Emission reflektiert wird und das verstärkende Lichtwellenleiterstück in Signalrichtung durchläuft. Das verstärkende Lichtwellenleiterstück befindet sich in einem angeregten Zustand, da der Pumplaser unabhängig vom Eingang dieses pumpt und wegen des fehlenden Signals keine stimulierte Emission erfolgt. Das reflektierte Licht erreicht das verstärkende Lichtwellenleiterstück in diesem Zustand der maximalen Besetzungsinversion und löst dadurch die Freisetzung der gespeicherten Energie aus. Es kommt zur Emission eines Riesenimpulses.Based on measurements on optical connectors, the time course of the attenuation D, the reflection R and the input power P in the fiber-optic amplifier could be determined when the optical waveguide was interrupted, as shown in FIG. 2. The point of interruption is the starting point for reflections due to the jump in the refractive index that occurs there, so that the light of the spontaneous emission is reflected there and passes through the amplifying optical waveguide piece in the signal direction. The amplifying optical waveguide piece is in an excited state, since the pump laser pumps independently of the input thereof and, because of the missing signal, there is no stimulated emission. The reflected light reaches the reinforcing optical waveguide piece in this state of maximum population inversion and thereby triggers the release of the stored energy. A huge pulse is emitted.

Vergleichbar einem Effekt, der von Festkörperlasern wohlbekannt ist, wird für die Riesenimpulsemission auch der Begriff des Q-Switching oder der Güte-Schaltung verwendet. Für Halbleiterlaser beschreibt diesen Effekt z.B. Petermann, U. in "Laser Diode Modulation and Noise" Kluwer Academic Publishers, UT K Scientific Publisher, Tokyo 1988.Comparable to an effect well known from solid-state lasers, the term Q-switching or quality switching is also used for the giant pulse emission. For semiconductor lasers, this effect describes e.g. Petermann, U. in "Laser Diode Modulation and Noise" Kluwer Academic Publishers, UT K Scientific Publisher, Tokyo 1988.

Die Erfindung beruht auf der Erkenntnis, daß die auftretende Reflexion R erst nach einer Verzögerungszeit τ auftritt, nach dem die Eingangsleistung durch die Vergrößerung der Dämpfung D abgefallen ist. Dadurch ist es erfindungsgemäß möglich, aus der Eingangsleistung ein Steuersignal abzuleiten.The invention is based on the knowledge that the occurring reflection R only occurs after a delay time τ after which the input power has dropped due to the increase in the damping D. This makes it possible according to the invention to derive a control signal from the input power.

Die erfindungsgemäße Funktion der Überwachungsvorrichtung besteht darin, sobald die Eingangsleistung des faseroptischen Verstärkers einen bestimmten Schwellenwert unterschreitet, den Stromweg oder den Lichtweg des Pumplasers innerhalb der Zeit τ zu unterbrechen. Messungen haben ergeben, daß die Zeit τ etwa 1 ms beträgt und daher ausreichend lang für ein rechtzeitiges Abschalten des Pumplasers oder ein rechtzeitiges unterbrechen des Lichtweges des Pumplasers ist.The function of the monitoring device according to the invention is to interrupt the current path or the light path of the pump laser within the time τ as soon as the input power of the fiber optic amplifier falls below a certain threshold value. Measurements have shown that the time τ is approximately 1 ms and is therefore sufficiently long for the pump laser to be switched off in good time or the pump laser light path to be interrupted in good time.

Ein Ausführungsbeispiel, wie das von der Eingangsleistung abgeleitete optische Signal weiterverarbeitet wird, ist in Fig. 3 gezeigt. Vom Ausgang des faseroptischen Kopplers gelangt es auf einen Photodetektor 71. Dessen elektrisches Ausgangssignal wird von einem Verstärker 72 verstärkt und einem Schwellenwert-Schalter 73 zugeführt, der die Ausgangsspannung U des Verstärkers mit einer Referenzspannung Uref vergleicht. Fällt die Verstärkerausgangsspannung unter eine Schwelle, die durch die Referenzspannung gegeben ist, gibt die Überwachungsvorrichtung, die aus den Komponenten 71, 72 und 73 besteht, ein Steuersignal ab. Ein anschließender Verstärker 9 steuert damit einen Transistor 10, der im Stromweg des Pumplasers 4 liegt. Dadurch ist der Stromweg des Pumplasers unterbrechbar und damit die Lichtemission des Pumplasers abschaltbar.An exemplary embodiment of how the optical signal derived from the input power is processed is shown in FIG. 3. From the output of the fiber optic coupler it arrives at a photodetector 71. Its electrical output signal is amplified by an amplifier 72 and fed to a threshold switch 73 which compares the output voltage U of the amplifier with a reference voltage U ref . Does that fall Amplifier output voltage below a threshold, which is given by the reference voltage, outputs the control device, which consists of components 71, 72 and 73, a control signal. A subsequent amplifier 9 thus controls a transistor 10 which is in the current path of the pump laser 4. As a result, the current path of the pump laser can be interrupted and the light emission of the pump laser can be switched off.

Alternativ zur Abschaltung des Pumplasers ist in Fig. 4 eine Möglichkeit gezeigt, bei der die Überwachungsvorrichtung 7 einen optischen Schalter 12 so steuert, daß dieser den Lichtweg des Pumplasers unterbricht. Ein solcher optischer Schalter ist beispielsweise in Siemens telcom report 6, April 1983, Beiheft "Nachrichtenübertragung mit Licht", S. 205 - 208 gezeigt.As an alternative to switching off the pump laser, FIG. 4 shows a possibility in which the monitoring device 7 controls an optical switch 12 in such a way that it interrupts the light path of the pump laser. Such an optical switch is shown, for example, in Siemens telcom report 6, April 1983, supplement "Message transmission with light", pp. 205-208.

Claims (4)

Optisches Nachrichtenübertragungssystem mit mindestens einem faseroptischen Verstärker, der ein sein optisches Eingangssignal verstärkendes Lichtwellenleiterstück (3), eine Pumplicht-Quelle (4) und Mittel (5) zum Einkoppeln eines von der Pumplicht-Quelle erzeugten Pumplichtes in das verstärkende Lichtwellenleiterstück (3) enthält,
dadurch gekennzeichnet, daß eine Überwachungsvorrichtung (7) vorhanden ist, die bei Abfallen der optischen Eingangsleistung eine Einstrahlung von Pumplicht aus der Pumplicht-Quelle (4) in das verstärkende Lichtwellenleiterstück (3) verhindert.Optical communication system with at least one fiber-optic amplifier, which contains an optical waveguide section (3) amplifying its optical input signal, a pump light source (4) and means (5) for coupling a pump light generated by the pump light source into the amplifying optical waveguide section (3),
characterized in that a monitoring device (7) is present which prevents pump light from the pump light source (4) from entering the amplifying optical waveguide piece (3) when the optical input power drops. Optisches Nachrichtenübertragungssystem nach Anspruch 1,
dadurch gekennzeichnet, daß die Überwachungsvorrichtung (7) den Stromweg der Pumplicht-Quelle (4) unterbricht.Optical communication system according to claim 1,
characterized in that the monitoring device (7) interrupts the current path of the pump light source (4). Optisches Nachrichtenübertragungssystem nach Anspruch 1,
dadurch gekennzeichnet, daß die Überwachungsvorrichtung (7) den Lichtweg der Pumplicht-Quelle (4) unterbricht.Optical communication system according to claim 1,
characterized in that the monitoring device (7) interrupts the light path of the pump light source (4). Optisches Nachrichtenübertragungssystem nach Anspruch 1,
dadurch gekennzeichnet, daß die Überwachungsvorrichtung (7) einen Photodetektor (71) mit nachgeschaltetem Verstärker (72) enthält und außerdem einen Schwellenwert-Schalter (73), der bei einer Verstärkerausgangsspannung, die kleiner als eine Referenzspannung ist, ein Steuersignal abgibt.Optical communication system according to claim 1,
characterized in that the monitoring device (7) contains a photodetector (71) with a downstream amplifier (72) and also a threshold switch (73) which outputs a control signal at an amplifier output voltage which is less than a reference voltage.
EP93106767A 1992-05-09 1993-04-27 Optical telecommunications system with monitoring device for avoiding strong pulses Expired - Lifetime EP0569769B1 (en)

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DE4215338A DE4215338A1 (en) 1992-05-09 1992-05-09 Optical communication system with monitoring device to avoid giant impulses

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NZ247497A (en) 1995-11-27
AU663372B2 (en) 1995-10-05
ES2128366T3 (en) 1999-05-16
DK0569769T3 (en) 1999-08-30
DE59309267D1 (en) 1999-02-18
US5475521A (en) 1995-12-12
JPH06120899A (en) 1994-04-28
AU3830593A (en) 1993-11-11
CA2094867A1 (en) 1993-11-10
DE4215338A1 (en) 1993-11-11

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